In the past, driver assistance systems have become widely available for large numbers of vehicles due to decreasing costs of such driver assist systems. One example of such driver assistance systems are vehicle navigation systems.
A vehicle navigation system possesses an inherent accuracy of position determination for the vehicle it is installed in. Due to usage of external positioning systems, such as the Global Positioning System (GPS), this accuracy is limited to the accuracy of the positioning system. In case of GPS, a positional error is in the order of 10 meters, which is usually accurate enough for highways or rural areas. However, in case of densely built areas, such as cities, turning points, such as roads, crossings and/or roundabouts, may have distances from one another in the order of 10 meters or even below. In such a case, an inherent accuracy of 10 meters may be insufficient.
Vehicle navigation systems or parts thereof (such as positioning components) may be in communication with Advanced Driver Assistance Systems (ADASs). An ADAS may, for example, be configured to change a shape of a vehicle spotlight at crossings, to change the direction of the vehicle spotlight on wiggly roads or to change the current gear selection. To perform such and other actions, the current vehicle position should be known with high accuracy. However, also ADASs inherently suffer from the positioning inaccuracy described above.
FIG. 1 shows a plan view of a vehicle 10 travelling along a road. As is shown in FIG. 1, there are basically two different types of error in relation to the true position of the vehicle on the road the vehicle is driving on.
Error Along the Street/Road:
Basically, this type of error covers an error caused by positioning systems (such as the GPS) in a direction substantially parallel to the longitudinal view axis of the vehicle (hence, of the driver). In other words, this type of error covers a fuzziness of the vehicle position in front of/behind the vehicle.
The error along the road can be compensated by using map data accessible to the vehicle navigation system or ADAS (e.g., after turning on a crossing or on a wiggly road).
Error Across the Street/Road:
This type of error basically covers an error caused by positioning systems in a direction substantially perpendicular to the longitudinal view axis of the vehicle (hence, of the driver), or a direction parallel to the vertical view axis of the vehicle. In other words, this type of error covers a fuzziness of the vehicle position left/right of the vehicle.
The error across the road can be reduced based on map data, since it can be reasonably assumed that the vehicle travels on the road and not in the range of fuzziness left/right of the road. Further, if taking into account the driving direction and the driving road side (e.g., right road side in countries such as Germany, or left road side in countries such as England), an assumption can be made on the side of the road the vehicle actually travels on, and hence the error across the road can be further reduced.